Thermally robust and porous noncovalent organic framework with high affinity for fluorocarbons and CFCs

摘要

Metal-organic and covalent organic frameworks are porous materials characterized by outstanding thermal stability, high porosities and modular synthesis. Their repeating structures offer a great degree of control over pore sizes, dimensions and surface properties. Similarly precise engineering at the nanoscale is difficult to achieve with discrete molecules, since they rarely crystallize as porous structures. Here we report a small organic molecule that organizes into a noncovalent organic framework with large empty pores. This structure is held together by a combination of [N-H center dot center dot center dot N] hydrogen bonds between the terminal pyrazole rings and [pi center dot center dot center dot pi] stacking between the electron-rich pyrazoles and electron-poor tetra-fluorobenzenes. Such a synergistic arrangement makes this structure stable to at least 250 degrees C and porous, with an accessible surface area of 1,159 m(2) g(-1). Crystals of this framework adsorb hydrocarbons, CFCs and fluorocarbons-the latter two being ozone-depleting substances and potent greenhouse species-with weight capacities of up to 75%.